Loading...
Search for:
dendrite-arm-spacing
0.006 seconds
Investigation on the Effect of Cooling Rate on the Solidification Behavior and Microstructure of Al 713 alloy using Thermal Analysis Technique
, M.Sc. Thesis Sharif University of Technology ; Varahram, Nasser (Supervisor)
Abstract
Considering the limited number of works on investigation of solidification characteristics of Al-Zn-Mg-Cu cast alloys as well as the applications of this alloy system in aerospace industries, the solidification conditions of Al 713 alloy were investigated in this study. In order to achieve this goal, a number of experiments were designed and conducted including quantometry, thermal analysis, metallography and hardness measurements. In this thesis, effects of cooling rate on secondary dendritic arms spacing as well as solidification parameters including nucleation temperature, solidification time and temperature range, dendrite coherency point and formation temperature of intermetallic...
Silicon morphology modelling during solidification process of A356 al alloy
, Article International Journal of Cast Metals Research ; Volume 25, Issue 1 , 2012 , Pages 53-58 ; 13640461 (ISSN) ; Mazahery, A ; Davami, P ; Razavi, M ; Sharif University of Technology
Abstract
In this paper, an introduction of the finite element approach to microstructure based modelling is provided, and the primary and secondary dendrite arm spacings of A356 alloy in the solidification process are simulated. The simulated results of dendrite morphology and the experimental measurements are presented and compared with the investigations of other researchers, which confirmed the accuracy of this model in its ability to predict the dendrite arm spacing. Each of the length scales, including silicon rod diameter and spacing, is discussed in detail. Analytical equations are generated for the length scales and incorporated in the Sharif University Technology academic software for the...
A Mathematical Model to Prediction of the Formation of Microporsities in Aluminium Alloy Cast Parts
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor) ; Davami, Parviz (Supervisor)
Abstract
Today, application of aluminium alloys in industries is developing. And this is because of some specification of these alloys like high proportion of the Strength per weight. One of the most useful alloys of this alloy group is A356 alloy that contain 7 % Silicon and 0.4 Percent of magnesium, this alloy because of cast ability, heat treat ability specification is use developing in air and automotive industries. But usage of this alloys combined with some difficulties like low fluidity and formation of shrinkage and gas porosities in this alloys. In present work with programmer software Visual Fortran, based on Finite difference method, a simulation model has been developed, can solve heat...
Investigating the Possibility of Elimination of Nickel and Replacement of Copper and Silicon Instead of that in A336 Casting Alloy Used in Automotive Pistons
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor)
Abstract
In this research the effect of Si, Cu and Ni alloying elements on the structure and mechanical properties of the A336 alloy is investigated. Expriments were done in two situations, casting and heat treated and the results for all samples with different amount of alloying elements are compared and the effect of heat treating is also investigated. Results show that with increasing the amount of Si and Cu and decreasing the amount of Ni strength and hardness of the cast alloy are 134 MPa and 65 HB and they increase to 187 MPa and 89 HB in heat treated alloy. The elongation and coefficient of linear expansion are decreased from 2.3% and 21.94 μm/m.K to 1.1% and 21.62 μm/m.K. Also the T6 heat...
A mathematical model for prediction of microporosity in aluminum alloy A356
, Article International Journal of Advanced Manufacturing Technology ; Volume 64, Issue 9-12 , April , 2013 , Pages 1313-1321 ; 02683768 (ISSN) ; Hatami, N ; Varahram, N ; Davami, P ; Shabani, M. O ; Sharif University of Technology
2013
Abstract
In the present work, a mathematical model was developed based on finite difference method to predict the microporosity distribution in A356 aluminum alloy casting. Heat, mass, and gas conservation equations were solved in this model. Moreover, Darcy's equation was considered in the mushy zone. Results show that the distribution and concentration of microporosities in cast parts vary with both cooling rate and initial gas content. Simulation results were compared with experimental data where proportionally good agreement with experimental results was found. Finally, a complex cast part was simulated presenting the ability of the model to predict the porosities in industrial cast parts
Microstructure and mechanical properties of dissimilar nickel-based superalloys resistance spot welds
, Article Materials Science and Engineering A ; Volume 773 , 2020 ; Pouranvari, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
This paper addresses the factors affecting the mechanical properties of dissimilar resistance spot welds between Nimonic 263 and Hastelloy X nickel-based superalloys. The fusion zone (FZ) of the dissimilar weld displayed higher hardness values compared to the base metals which can be attributed to (i) the formation of Mo-rich carbide in the interdendritic zone due to positive segregation behavior of Mo and C during non-equilibrium solidification of the weld, (ii) the enhanced solid solution strengthening due to mixing of the base metals, and (iii) the formation of ultra-fine dendritic structure in the FZ due to ultra-fast cooling rate of the resistance spot welding. Formation of...
Microstructural evolution of Al-20Si-5Fe alloy during rapid solidification and hot consolidation
, Article Rare Metals ; Volume 28, Issue 6 , 2009 , Pages 639-645 ; 10010521 (ISSN) ; Vahidi, M ; Simchi, A ; Davami, P ; Sharif University of Technology
Abstract
Al-20Si-5Fe melt was rapidly solidified into particles and ribbons and then consolidated to near full density by hot pressing at 400°C/250 MPa/1 h. According to the eutectic-growth and dendritic-growth velocity models, the solidification front velocity and the amount of undercooling were estimated for the particles with different sizes. Values of 0.43-1.2 cm/s and 15-28 K were obtained. The secondary dendrite arm spacing revealed a cooling rate of 6 × 105 K/s for the particles with an average size of 20 μm. Solidification models for the ribbons yielded a cooling rate of 5 × 107 K/s. As a result of the higher cooling rate, the melt-spun ribbons exhibited considerable microstructural...